The present method of constructing a bridge or a span between two points separated, by water, chasm or the like, is to construct a truss structure between the points, upon which decking forming a surface for a road or other way may be placed. More widely separated points usually require suspension of cables from towers located at each of the end points. A pan is supported by additional vertical cables attached to the longitudinal, principal cables. Long spans require additional supporting towers intermediate of the ends points of the span. A roadway or the like is then constructed on the suspended pan. The roadway is generally a stiff substructure of relatively rigid struts and beams. The present invention contemplates a new method of spanning two points, which method reduces the time, expense and difficulty generally associated with methods known heretofore by utilizing an inflatable sheath to form a temporary arch spanning the two points, which arch is of sufficient strength to support construction of a structural frame between the two points.